Interstitial Lung Diseases

On this page

ILD Overview - The Lung Labyrinth

  • Definition: Diverse group of diffuse parenchymal lung diseases affecting the interstitium, causing inflammation and/or fibrosis.
  • Key Symptoms: Progressive exertional dyspnea, persistent dry cough.
  • Key Sign: Bibasilar fine inspiratory crackles ('Velcro rales'). Clubbing possible.
  • Basic Pathophysiology: Alveolitis → Chronic Inflammation → Fibrosis → Impaired gas exchange, stiff lungs.
  • PFTs: Restrictive pattern: ↓TLC, ↓DLCO; normal or ↑ $FEV_1/FVC$ ratio.
  • Broad Classification:
    • Known causes: Drugs (amiodarone, bleomycin), CTD (RA, SSc), environmental (asbestosis, silicosis).
    • Idiopathic Interstitial Pneumonias (IIPs): e.g., IPF, NSIP.
    • Granulomatous: Sarcoidosis, Hypersensitivity Pneumonitis (HP).
    • Rare ILDs. Alveolar-capillary unit and fibrosis in ILD

⭐ Bibasilar 'Velcro' crackles are a characteristic auscultatory finding in many ILDs, especially IPF.

IPF - Scarred Scenery

  • Most common, severe Idiopathic Interstitial Pneumonia (IIP).
  • Affects older adults (>60 yrs), M>F predominance.
  • Pathology: Usual Interstitial Pneumonia (UIP) pattern (hallmark: spatial & temporal heterogeneity).
  • HRCT Chest (essential for diagnosis):
    • Bilateral, basal, subpleural reticulation.
    • Honeycomb cysts.
    • Traction bronchiectasis.
    • Absence of: extensive Ground Glass Opacities (GGO), nodules, consolidation.
  • Diagnosis of exclusion: Rule out Connective Tissue Disease (CTD), drug toxicity, chronic Hypersensitivity Pneumonitis (HP).
  • Prognosis: Poor; median survival 3-5 years.
  • Management:
    • Antifibrotics: Pirfenidone, Nintedanib (slow Forced Vital Capacity (FVC) decline).
    • Supportive: O2, pulmonary rehabilitation.
    • Lung transplant.
  • HRCT chest showing UIP pattern with honeycombing
  • ⭐ > The UIP pattern on HRCT, characterized by subpleural, basal predominant honeycombing, is crucial for IPF diagnosis.

Sarcoidosis - Granuloma Galaxy

  • Unknown etiology multisystem disorder; hallmark: non-caseating granulomas.
  • Pulmonary involvement: >90% of cases.
  • CXR Staging (Scadding):
![CXR Sarcoidosis Stages I-IV](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Internal_Medicine_Pulmonology_Interstitial_Lung_Diseases/30f05fd5-1ed8-465f-a93d-c21ac9db429c.png)
  • Extrapulmonary sites: Skin (erythema nodosum, lupus pernio, maculopapular rash), eyes (uveitis, conjunctivitis), lymph nodes, liver, spleen, heart, nervous system.

⭐ Löfgren's syndrome (acute arthritis, erythema nodosum, and bilateral hilar lymphadenopathy) is an acute form of sarcoidosis with a good prognosis.

  • Diagnosis: Compatible clinical/radiological findings + histological evidence of non-caseating granulomas + exclusion of other granulomatous diseases.
  • Lab findings: ↑ Serum Angiotensin-Converting Enzyme (ACE) (non-specific, reflects granuloma load). Hypercalcemia/hypercalciuria (due to macrophage $1\alpha$-hydroxylase activity).

Other Key ILDs - Diverse Diffusopathies

  • Hypersensitivity Pneumonitis (HP): Immune reaction to inhaled organic antigens (Farmer's lung, Bird fancier's lung).
    • Acute, subacute, chronic (can → fibrosis).
    • HRCT: Acute/Subacute - centrilobular ground-glass nodules, mosaic attenuation. Chronic - fibrosis. HRCT Nonfibrotic Hypersensitivity Pneumonitis Findings
    • Rx: Antigen avoidance, corticosteroids.
  • Connective Tissue Disease-Associated ILD (CTD-ILD): Common in Scleroderma (SSc), Rheumatoid Arthritis (RA), Polymyositis/Dermatomyositis (PM/DM).
    • Patterns: NSIP (SSc), UIP (RA-ILD, poorer prognosis), OP.
  • Pneumoconioses:
    • Silicosis: Silica dust. Upper lobe nodules, Progressive Massive Fibrosis (PMF). ↑ TB risk.

      ⭐ 'Egg-shell' calcification of hilar lymph nodes on chest X-ray is highly suggestive of silicosis.

    • Asbestosis: Asbestos fibers. Lower lobe fibrosis, pleural plaques. ↑ risk of lung cancer & mesothelioma.

High‑Yield Points - ⚡ Biggest Takeaways

  • IPF: UIP pattern (honeycombing, traction bronchiectasis) on HRCT; treat with Pirfenidone/Nintedanib.
  • Sarcoidosis: Non-caseating granulomas, bilateral hilar lymphadenopathy, ↑ACE, hypercalcemia; Lofgren's syndrome.
  • Hypersensitivity Pneumonitis: Antigen exposure (farmer's/bird fancier's lung); antigen avoidance is crucial.
  • CTD-ILD: Common with scleroderma, RA; NSIP pattern is frequent.
  • Pneumoconioses: Occupational dusts (silicosis: ↑TB risk; asbestosis: mesothelioma).
  • ILDs show restrictive PFTs (↓TLC, ↓FVC, ↓DLCO); key drug causes: Amiodarone, Bleomycin, Methotrexate.

Practice Questions: Interstitial Lung Diseases

Test your understanding with these related questions

Which of the following is NOT a characteristic feature of sarcoidosis?

1 of 5

Flashcards: Interstitial Lung Diseases

1/10

Which subtypes of idiopathic interstitial pneumonia are associated with smoking?_____

TAP TO REVEAL ANSWER

Which subtypes of idiopathic interstitial pneumonia are associated with smoking?_____

Respiratory bronchiolitis associated ILD (RB-ILD) and Desquamative interstitial pneumonia (DIP)

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial